The need to recycle polymeric materials, especially from the expanding post consumer waste stream, is increasing as demands increase and available landfill sites continue to decrease. Polymeric materials are a small, but growing fraction of the post consumer waste stream entering landfill sites. Polymeric materials can, of course, be recycled and various programs and investigations are underway to increase the amount of recycled polymers and find useful products where these materials can provide a needed and useful function. Polymeric constituents from the post consumer waste stream represent a new and unique source of materials for polymer-type applications. The recovery of polymers from this source yields many diverse type of products including a wide range of polymer mixtures from almost pure constituents (e.g. poly(ethylene terephthalate) from carbonated beverage containers and HDPE from milk bottles) to mixed classes (e.g. low density bottle scrap based on primarily polyolefins, high density bottle scrap containing primarily poly(ethylene terephthalate) and poly(vinyl chloride)), to mixtures of all bottle materials and finally mixtures of all polymer scrap including poly(vinylidene chloride), ethylene/vinyl alcohol copolymers, cellulosic products (e.g. cellophane), high acrylonitrile copolymers (such as Barex (Sohio:BP) based on acrylonitrile/methyl acrylate used for food packaging) and the like. Many of the polymers found in post consumer polymer scrap have solubility parameters greater than 10, for example one of the most common constituents, poly(ethylene terephthalate) has a solubility parameter of 10.6. The mechanical properties of commingled polymers of widely ranging compositions are quite poor and applications for commingled polymers generally fall in lowest range of cost/performance requirements for materials. These applications include flower pots, posts, lumber, fence slats, etc. In order to improve the properties of commingled polymer waste, Paul et.al. in Mod. Plast., 58, 60, (1981) noted that the styrene-ethylene/butylene-styrene ABA block copolymer commonly referred to as Kraton G yielded improved mechanical properties when admixed with polymer mixtures similar to that present in post consumer polymer waste.
Various processes for conversion of polymeric materials into fine fibers exist to meet the requirements of a myriad of applications. These processes include melt-blowing processes to yield fibrous materials, melt spinning technology, and polymer blend processes followed by extraction of one of the components.
Miller and Merriam note in U.S. Pat. No. 3,097,991 that a polymer pulp can be made by extrusion of immiscible polymers followed by a paper beating type operation to separate the immiscible fibers. These fibers could then be dispersed in water and a polymer pulp could be made. The use of a solvent for one of the constituents of the immiscible polymer blend to liberate the fibers was noted in a similar patent by Merriam and Miller (U.S. Pat. No. 3,099,067). This patent discussed methods to make ultra-fine fibers of polyethylene, polychlorotrifluoroethylene, or polyamides. U.S. Pat. No. 3,382,305 discloses a process for the formation of oriented materials containing microfibers by blending at least two incompatible fiber-forming polymers via extrusion followed by drawing (orienting) and optionally dissolving one of the polymers from the resultant fibrous material. None of these references discuss or disclose the potential utility of polymer scrap or the utility of poly(vinyl alcohol) as a water soluble matrix for the production of fine fibers.
Japanese patent application Showa 47-67754 discloses a method for manufacturing fine fibrils containing poly(vinyl alcohol). They disclose a method involving mixing poly(vinyl alcohol) with 20-95% of one or more polymers with a solubility parameter of 10 (cal/cc).sup.1/2 or less and extruding and drawing the extruded mixture. The resultant drawn article is then beaten in water containing an inorganic salt to prevent the foaming and extraction of the poly(vinyl alcohol). They note that mixtures of polyethylene and polypropylene can be utilized in this process. They do not disclose the potential of using post-consumer polymer scrap nor the use of defoaming agents. Additionally, the disclosed process specifically does not remove the PVOH from the resultant fibers, in fact, the patent takes procedures to prevent removal of poly(vinyl alcohol).
Japanese Patent Application No. Showa 44-20869 discloses the method of manufacturing water-containing poly(vinyl alcohol) powder and a thermoplastic linear polymer powder by mixing them, followed by thermal fusion and extrusion. Molded articles were the subject of this invention and neither extraction of the poly(vinyl alcohol) nor fiber production from the extracted blend was carried out.